POP3（Post Office Protocol version 3）is a protocol used to download mail from the mail server to the local device. After downloading, the mail on the server is usually deleted or marked as read. It is suitable for users who check mail occasionally through a single device. The operation of POP3 is one-way, which means that the client’s operations are not reflected on the server.
The default port is 110, but it is not secure, so it is recommended to use port with SSL/TLS encryption, such as 995(SSL).